Hong Kong ? Dozens more people at a Hong Kong apartment complex contracted a flu-like disease to bring the number there to 213, health officials said Monday, as the mystery illness with no known treatment continued its spread.

Hong Kong’s health secretary, Dr. Yeoh Eng-kiong, announced the big rise in severe acute respiratory syndrome, or SARS, cases just hours after authorities imposed a tight quarantine on one bloc of apartments at the Amoy Gardens complex.

He said 88 new cases were diagnosed at the building complex to add to 125 other cases, bringing the total to 213.

The report came as the World Health Organization said that SARS has killed at least 54 people worldwide, with the majority of cases in Hong Kong and China. That figure does not include three more deaths reported Sunday, one each in Hong Kong, Toronto and Singapore. More than 1,600 people have been infected worldwide.

Singapore’s health minister, Lim Hng Kiang, said the disease may spread more easily than first believed, with some people found to be more infectious than others. Labeled as “super infectors,” they can infect as many as 40 others, he said.

“We run the risk of a huge new cluster of infected people, which could start a chain reaction,” Lim told a news conference.

Singapore said it would station nurses at its airport to examine all travelers arriving from infected areas, while Canada planned to screen those traveling abroad from Toronto, although no system was in place Sunday.

Yeoh said 107 of the sick people were from one section, Block E. He said officials believe the virus was brought to Amoy Gardens by a man infected at the Prince of Wales Hospital, where many of Hong Kong’s victims have fallen ill.

In Canada, meanwhile, another death was reported Sunday to bring the toll there to four. Officials earlier declared a health emergency in Toronto, located 50 miles from the U.S. border. U.S. health officials have reported 62 cases in the United States but no deaths.

About 100 probable or suspect cases have been reported in Canada. Officials have closed two hospitals to new patients, and hundreds of people have been quarantined in their homes.

Another possible case turned up in New Brunswick on Canada’s east coast, officials said Sunday, meaning the illness that originated in Asia may now reach across Canada. The New Brunswick case involves a school principal who recently traveled to China.